The same-sign top signature of R-parity violation

Baryonic R-parity violation could explain why low-scale supersymmetry has not yet been discovered at colliders: sparticles would be hidden in the intense hadronic activity. However, if the known flavor structures are any guide, the largest baryon number violating couplings are those involving the top/stop, so a copious production of same-sign top-quark pairs is in principle possible. Such a signal, with its low irreducible background and efficient identification through same-sign dileptons, provides us with tell-tale signs of baryon number violating supersymmetry. Interestingly, this statement is mostly independent of the details of the supersymmetric mass spectrum. So, in this paper, after analyzing the sparticle decay chains and lifetimes, we formulate a simplified benchmark strategy that covers most supersymmetric scenarios. We then use this information to interpret the same-sign dilepton searches of CMS, draw approximate bounds on the gluino and squark masses, and extrapolate the reach of the future 14 TeV runs.Comment: 32 pages, 12 figures, 3 tables, 1 appendi

Financial Conditions Indexes for Canada

The authors construct three financial conditions indexes (FCIs) for Canada based on three approaches: an IS-curve-based model, generalized impulse-response functions, and factoranalysis. Each approach is intended to address one or more criticisms of the monetary conditions index (MCI) and existing FCIs. To evaluate their three FCIs, the authors consider five performance criteria: the consistency of each FCI's weight with economic theory, its graphical ability to predict turning points in the business cycle, its dynamic correlation with output, its in-sample fit in explaining output, and its out-of-sample performance in forecasting output. Using monthly data, the authors find, in general, that housing prices, equity prices, and bond yield risk premiums, in addition to short- and long-term interest rates and the exchange rate, are significant in explaining output from 1981 to 2000. They also find that the FCIs outperform the Bank of Canada's MCI in many areas.Monetary and financial indicators; Monetary conditions index

Three-generation baryon and lepton number violation at the LHC

One of the most puzzling questions in particle physics concerns the status of the baryon (B) and lepton (L) quantum numbers. On the theoretical side, most new physics scenarios naturally lead to their non-conservation and some amount of violation is actually needed to explain the baryon asymmetry of the Universe. On the experimental side, low-energy constraints such as those on proton decay are so stringent that it is generally believed that no B and L violation will ever be seen in laboratories. We observe that this apparent contradiction, however, disappears when the flavor symmetries involving all three generations are taken into account. We then identify model-independent classes of B and/or L violating six-fermion-based processes that indeed simultaneously satisfy low-energy constraints and produce clearly identifiable signals at the LHC. Finally, through simplified models, we study two classes characterized by (\Delta B;\Delta L) = (\pm 1;\pm 3) and (\pm 2; 0), that lead to particularly striking signatures (t \mu^+ e^+ and \bar t \bar t + jets, respectively).Comment: 5 pages, 2 figures, 1 table; v2: version to appear in Phys.Lett.

A Kaluza-Klein Model with Spontaneous Symmetry Breaking: Light-Particle Effective Action and its Compactification Scale Dependence

We investigate decoupling of heavy Kaluza-Klein modes in an Abelian Higgs model with space-time topologies $\mathbb{R}^{3,1} \times S^{1}$ and $\mathbb{R}^{3,1} \times S^{1}/\mathbb{Z}_{2}$. After integrating out heavy KK modes we find the effective action for the zero mode fields. We find that in the $\mathbb{R}^{3,1} \times S^{1}$ topology the heavy modes do not decouple in the effective action, due to the zero mode of the 5-th component of the 5-d gauge field $A_{5}$. Because $A_{5}$ is a scalar under 4-d Lorentz transformations, there is no gauge symmetry protecting it from getting mass and $A_{5}^{4}$ interaction terms after loop corrections. In addition, after symmetry breaking, we find new divergences in the $A_{5}$ mass that did not appear in the symmetric phase. The new divergences are traced back to the gauge-goldstone mixing that occurs after symmetry breaking. The relevance of these new divergences to Symanzik's theorem is discussed. In order to get a more sensible theory we investigate the $S^{1}/\mathbb{Z}_{2}$ compactification. With this kind of compact topology, the $A_{5}$ zero mode disappears. With no $A_{5}$, there are no new divergences and the heavy modes decouple. We also discuss the dependence of the couplings and masses on the compactification scale. We derive a set of RG-like equations for the running of the effective couplings with respect to the compactification scale. It is found that magnitudes of both couplings decrease as the scale $M$ increases. The effective masses are also shown to decrease with increasing compactification scale. All of this opens up the possibility of placing constraints on the size of extra dimensions.Comment: 35 pages, 6 figure

Forest management is driving the eastern North American boreal forest outside its natural range of variability

Fire is fundamental to the natural dynamics of the North American boreal forest. It is therefore often suggested that the impacts of anthropogenic disturbances (eg logging) on a managed landscape are attenuated if the patterns and processes created by these events resemble those of natural disturbances (eg fire). To provide forest management guidelines, we investigate the long-term variability in the mean fire interval (MFI) of a boreal landscape in eastern North America, as reconstructed from lacustrine (lake-associated) sedimentary charcoal. We translate the natural variability in MFI into a range of landscape age structures, using a simple modeling approach. Although using the array of possible forest age structures provides managers with some flexibility, an assessment of the current state of the landscape suggests that logging has already caused a shift in the age-class distribution toward a stronger representation of young stands with a concurrent decrease in old-growth stands. Logging is indeed quickly forcing the studied landscape outside of its long-term natural range of variability, implying that substantial changes in management practices are required, if we collectively decide to maintain these fundamental attributes of the boreal forest

The Adobe Frontier

The Adobe Frontier is a documentary film about Ronald Rael and Virginia San Fratello—together known as “Studio Rael San Fratello” —and their work connecting contemporary technology with the legacy of pottery making and adobe architecture in the Southwest United States

Reproducing and Resisting Whiteness in a Quasi-Desegregated Suburban High School: An Ethnographic Field Analysis.

I conduct ethnographic research in a quasi-desegregated high school to determine how the structure of the institution in relation with white students’ level of interaction with non-resident black students impacts their understanding of the racial hierarchy and their place within it. Bourdieu’s notions of field and capital provide the guiding theoretical framework for this dissertation and structured both the collection and interpretation of the data. The data were collected through participant observation and interviews with faculty, white students and students of color and suggests the fluidity of whiteness: white students with objectively similar backgrounds who inhabit the same physical location can develop different visions of whiteness and white privilege. Reproductive tendencies were noted among white students whose experiences led them to observe but not interact with black students and resistance was noted among white students whose friendship circles, athletic endeavors and romantic relationships found them in consistent and personal interaction with black students. In some cases resistance was nascent or marked by contradiction indicating that the institutional tendency toward reproduction was formidable. This dissertation contributes to the sociology of race by illuminating the ways in which whiteness is insinuated within the culture of an institution but simultaneously concealed from whites’ view and how this arrangement reproduces normative whiteness and regressive notions of the racial other. In demonstrating the deeply rooted and seemingly non-racial ways in which race operates within institutions and how this perpetuates and reinforces racialized notions of difference, this dissertation reveals how race continues to structure social life in the post-civil rights era. Furthermore, this dissertation complicates monolithic notions of whiteness by showing that there is variation in whites’ ability to apprehend the continuing salience of race and white privilege while identifying one mechanism—interaction—that serves to explain this variation. The dissertation concludes by considering recommendations for pedagogical practice and institutional change that could nurture the inchoate strains of resistance that are identified.PHDSociologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/100091/1/cgauthie_1.pd

Decoupling of Heavy Kaluza-Klein Modes In Models With Five-Dimensional Scalar Fields

We investigate the decoupling of heavy Kaluza-Klein modes in $\phi^{4}$ theory and scalar QED with space-time topology $\mathbb{R}^{3,1} \times S^{1}$. We calculate the effective action due to integrating out heavy KK modes. We construct generalized RGE's for the couplings with respect to the compactification scale $M$. With the solutions to the RGE's we find the $M$-scale dependence of the effective theory due to higher dimensional quantum effects. We find that the heavy modes decouple in $\phi^{4}$ theory, but do not decouple in scalar QED. This is due to the zero mode of the 5-th component $A_{5}$ of the 5-d gauge field. Because $A_{5}$ is a scalar under 4-d Lorentz transformations, there is no gauge symmetry protecting it from getting mass and $A_{5}^{4}$ interaction terms after loop corrections. In light of these unpleasant features, we explore $S^{1}/\mathbb{Z}_{2}$ compactifications, which eliminate $A_{5}$, allowing for the heavy modes to decouple at low energies. We also explore the possibility of decoupling by including higher dimensional operators. It is found that this is possible, but a high degree of fine tuning is required.Comment: 9 pages, no figures; sign error on equations 20, 36, 37; Added additional reference